Principial investigator:

Co investigator:

Summary:

In recent years it became evident that the climate of the Earth is not only determined by terrestrial, in particular anthropogenic, influences but also by external parameters. The evidence for these influences derives from numerous studies revealing to what extent solar radiation and energetic particles, particularly cosmic rays, correlate with terrestrial observables, like the production of cosmogenic isotopes, lightning, temperature, global cloud coverage, and, consequently, with the climate on the Earth. The question, however, is whether the solar radiation or the cosmic rays are the main agents regarding the external climate driving. With the proposed research we will perform a quantitative study in order to clarify the role of energetic particles on the II-year solar cycle but more important on long time scales. In our work we combine, for the first time, simulations of the changing heliospheric structure and the resulting galactic cosmic ray spectra close to the Earth with simulations of energetic particle interactions with the Earth's atmosphere. Our study will reveal the significance of the heliospheric transport for cosmic ray energy spectra. Thus, we will quantify to what extent the Sun and with it the heliosphere serves as a shield for the Earth's environment. The modulated cosmic spectra will be used to compute the production of cosmogenic isotopes in the Earth's atmosphere in order to check whether they are consistent with the data derived from ice core archives.